Centrifugal starting-switch for induction-motors.



H. G. REIST.

OENTRIFUGAL STARTING SWITCH FOR INDUGTION MOTORS. APPLICATION FILED MAY26, 1902.

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No. 735,151. PATENTED AUG. 4, 1903. H. G. REIST.

4 GENI'RIFUGAL STARTING SWITCH FOR INDUCTION MOTORS.

APPLICATION FILED MAY 26 1902.

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WiTHEssEs. I INVEHTOR V HENRY .REisT.

W BY ATTY.

UNITED STATES Patented August 4, 190

PATENT OFFICE.

HENRY e. REIST, OF sO HENE'oTADv, NEW YORK, ASSIGNOB TO GENERAL ELECTRICOOMPANY, A CORPORATION OF EW YORK.

CENTRIFUGAL STARTING-SWITCH FOR INDUCTION-MOTORS.

SPEGIFICATION forming part of Letters Patent No. 735,151, dated August4, 1903.

Application filed May 26,1902. Serialllo. 108,920. (.Nomodel.)

T0 aZZ whom it may concern..-

Be it known that I, HENRY G. REIsT, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements in CentrifugalStarting- Switches for Induction-Motors, of which the following is aspecification.

My invention relates to motor-starting devices, and more particularly tostarting devices for alternating-current electric motors in which thesecondary member is provided with a closed-circuited'induced windinghaving a resistance in circuit with the said winding for the purpose ofproducing a good start-.

ing torque, the said resistance being gradually cut out of circuit stepby step as the speed increases.

The object of my invention is to provide such a motor with an efficientcentrifugallyactuated starting device which will constitute animprovement on the device shown and described in the patent to L. Bell,No. 505,505, granted September26, 1893. To this end I employ in thepreferred embodiment of my invention a plurality of independent switchesmounted on the secondary member of the motor and arranged to be actuatedindependently and at difierent times by centrifugal force for thepurpose of cutting out the starting resistance step by step as the speedincreases.

My invention further comprises a novel switch construction, which willbe more fully explained hereinafter and set forth in the claims.

In the accompanying drawings, Figure 1 is an elevation of a motor towhich my invention has been applied, the casing of said motor beingpartially broken away. Fig. 2 is an end view of the armature or rotor ofsaid motor, on a larger scale, showing the manner in which the startingdevice is mounted thereon. Fig. 3 is a perspective detail View of onewindingw is mounted; C, the armature-shaft, and S the spider whichsupports the armature-ring, the said spider being keyed to the saidshaft at 70. Fastened to the spider S by means of the bolts g is anadditional frame H, upon which the starting-switches D, D, D, and D aremounted. Carried within the armature and bolted to the ringB thereof bymeans of the bolts b are the resistance-grids 6o 0", which areelectrically connected together and to the fixed contact-pieces n, 'n,and n of the starting-switches by means of the links m, m, and m andalso the connections 1), as shown in Fig. 2. In the three-phase windingshown there are three each of contact-pieces n, n, and 71?, those ineach set being mounted one behind the other, as shown in Fig. 3, andfastened to the frame H by means of bolts g. Attached to or integrallyformed with the contact-pieces n, n, and 91. respectively, are theswitch-contact faces f, f, and f with which the movable elements of theswitches D,D,D and D coact. Since these movable elements are similarlyconstructed, the construction of 75 but one will be described-namely,that of switch D. In Fig. 2 I have shown said switch in its normallyopen position against the stop d, which is carried by the frame H, whilein Fig. 3 Ihave shown in a perspective view the said switch in itsclosed position. Pivoted on the pin 10 which is carried by the frame H,is

a bell-crank lever, the arms of which make an obtuse angle with eachother. One arm, t,

of said bell-crank lever carries the switchbrushes or main and auxiliarycontact-makers a and a, which coact with the relatively fixed contactsf. Connected by means of the pin p 'to the other arm, t, of thebell-crank lever is a spring 6, which is fastened at its opposite end bymeans of an adjustable screwand-nut connection to the relatively fixedstud p, which projects from the frame H. The adjustable connectionbetween the spring 6 and the stud p is clearly shown in Fig. 3 andcomprises a nut 0, to which the spring is fastened, and ascre'w'or bolt0, which operates in both the stud p and the nut o, no thread being cuton the part of the screw which passes through stud p. The tension on theluu spring is changed by this means, and thereby the force required tomove said switch from its normally open position may be varied. Theauxiliary contact-pieces a, carrying the carbon button a are made ofresilient material and are mounted so as to make contact with therelatively fixed contact-facesfprior to and to break contact later thanthe main contact-brushes a. The brushes a, Fig. 3, are formed oflaminated conducting-strips removably mounted on the outer end of thearm t, it being understood that the arm if, on which the brushes a andthe removable auxiliary contact-pieces a are mounted, is formed of onepiece of conducting material, so that when the brushes a or a are incontact with the contact-faces f a short circuit between these faces ismade. The switches D and D have separate studs p for the springs 6,While the switches D and D use the same stud p for their springs e; butthis variation in construction doesnot affect the operations of eitherof said switches.

In Fig. 4 I have shown diagrammatically the electrical connectionsbetween the arma tore-windings w, (which are here shown in Yconnection,) the resistances r, and the switchcontact faces f, f, and frespectively. As will be seen, the resistances are respectivelyconnected in circuit with the windings of each phase and have theirouter ends grounded on the armature-spider or connected together in someother way. The resistances are divided into sections, and each sectionis connected with its corresponding contact-face in one of the sets f,f, or f Normally the winding w is close-circuited through its Yconnection at one end and through the resistances r and the groundconnections at the other end. If a short-circuiting switch is placedacross the contact-faces f part of the resistance r in each phase willbe short-circuited. If a switch is placed across the contacts f, more ofthe resistances are short-circuited, and if a switch is closed acrosseither of the sets of contacts f the entire resistance will beshortcircuited and the armature-windings closecircuited through thecontacts f and said switch.

In operation under normal conditions when the motor is at rest theswitches D, D, D and D are open and the movable member of the switchesrest against the stops or studs d. When the main-line switch is closed,the rotary field produced in the stator induces current in the rotor,the said current flowing through the windings w, which are connectedtogether in Y connection at one end and the resistance r and groundconnection at the other end. As the speed increases the centrifugalforce acting on the movable members of the starting switches becomessufficiently great to overcome the tension on the spring e of the switchD which has been previously set to operate at a predetermined speed. Asthe arm t, carrying the contact-makers a and Ct, moves outward theresisting force of the spring 2 becomes relatively less and less, due

to the peculiar manner in which the switch is mountedthat is,consideringa line drawn through the stud p and the pin 19 anda secondline drawn through the pins 10 and 12 As these lines approachparallelism the turning moment about the pin 19 due to the tension ofthe spring 6 is gradually reduced. Since the centrifugal force acting onthe arm t and contact-makers a and a remains practically constant duringthe movement of said switch, it will be seen that the switch will closewith a snap action against the relatively fixed contact-faces f and willremain closed even though the speed of the rotor drops considerably-thatis to say, it requires less force to maintain said switch in its closedposition than is required to start it from its open position with thearm 25 resting against the stop d. When the switch D has beenclosed,.equal amounts of the resistances r in each phase are shortcircuited and the rotor increases in speed. When the speed at which theswitch D has been set to operate has been reached, the said switchcloses suddenly, more resistance is short-circuited, and the rotor isfurther increased in speed. When a predetermined higher speed isreached, the switches D and D operate simultaneously, thereby shortcircuiting all the resistances r and allowing the rotor to rise to itsmaximum speed.

By the use of switches of the construction herein disclosed the motorwill run with the resistance all out out, even under an overloadsufficient to cause the'speed to drop materially.

One switch of the proper size to carry the current which is induced inthe winding to when the motor is running at normal working speed wouldbe sufficient to perform the function which is now performed by theswitches D and D acting simultaneously. Two switches, however, have beenused in the modification shown, since it allows a more symmetrical andevenly-balanced construction and allows the switch to be made lighterand more compact.

While I have shown and described my invention as applied to athree-phase induction-motor using four switches, I do not limit myselfto any particular number of phases or any particular number of switchesor to an alternating-current motor.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. In a motor-starting device, a plurality of switches operativelyconnected with the rotatable member, and means for adjusting saidswitches so that they will operate independently and successively as thespeed of the rotatable member increases.

2. In a motor-starting device, a plurality of centrifugally-actuatedswitches carried by the rotary member of the motor and adjusted tooperate successively as the speed of said member increases.

3. In an electric motor having a closed-circuited armature-winding, thecombination with resistance in circuit with said winding, saidresistance being divided into sections,

of a plurality of independent switches operatively connected with thearmature, said switches being independently adjustable to operateautomatically at any predetermined speed, and adapted to short-circuitthe successive sections of said resistance as the speed increases.

4. In a multiphase electric motor having a closed-circuitedarmature-winding, the combination with resistance in each phase of saidWinding, said resistance being divided into sections, of independentcentrifugally-actuated switches operatively connected with the armature,said switches being adjusted to operate independently to short-circuitcorresponding sections of said resistance in the several phasessimultaneously at certain predetermined speeds and the successivesections of said resistances as the speed increases.

5. In a multiphase electric motor having a closed-circuitedarmature-Winding, the combination with resistance in each phase of saidwinding, of a single switch operatively connected with the armature andadapted to opcrate automatically to short-circuit the reoperativelyconnected with the armature and 1 adapted to short-circuit theresistance in the several phases simultaneously when a certain speed isreached, the said switch being so constructed and arranged that agreater force is required to start the switch from its normally openposition than is required to maintain the switch in its closed position,and means for adjusting said switch so that it will operate at adifferent speed.

In witness whereof I have hereunto set my hand this 23d day of May,1902.

HENRY REIST.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

